redisdb: correct default ssl_cert_reqs

[wbobeirne]

What does this PR do?

Fixes the config.yaml documentation to correctly show that the default when not specifying ssl_cert_reqs is 2 (require)

Motivation

I was getting SSL errors that I didn't expect when adding a configuration for redis on Heroku, since Heroku requires you not verify the self-signed certificates they use for Redis. After some digging, I realized that the actual default for ssl_cert_reqs is to require them: https://redis-py.readthedocs.io/en/stable/#redis.Redis

Additional Notes

N/A

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[kayayarai]

No docs review required